Electrically energized lifting magnet



Feb. 25, 1958 s. G. INJESKI, JR 2,825,011

ELECTRICALLY ENERGIZED LFTING MAGNET Filed June 29, 1955 nited States Patent() 6 Claims. (Cl. 317-123) Wis., assgnor to Dings Milwaukee, Wis., a corpora- The present invention relates in general to improvements in the art of transferring magnetic materials from place to place, and relates more specifically to improvements in the construction and operation of electrically energized and universally movable lifting magnets for ferrous scrap or the like.

The primary object of my invention is to provide an improved electrically energized lifting magnet which is especially adapted to handle irregular shaped and sharp pieces of material such as scrap iron, and wherein the energizing structure is effectively protected against possible damage whenever the electric energizing current is interrupted.

Lifting magnets are ordinarily employed to transfer ferrous materials from one locality to another while the magnet units are suspended from cranes or booms by means of chains or cables adapted to lift and lower the magnets and to move them laterally. When these lifting magnets are of the electrically energized type, the cur rent for energizing the magnet windings or coils, is usually supplied through a flexible conductor cord or cable which is c-ooperable with a reel on the magnet suspension structure so as to take up excess slack while the magnet is being moved about. In order to protect the insulation for the energizing coils of such magnets when operating with power consumptions above 700 watts, against possible damage due to excessive counter electro-motive force generated in these coils when the current supply is suddenly interrupted, a high resistance having low power consumption at low voltage is customarily applied across the terminals of the control switch whenever the latter is opened, near the operators station located remote from the magnet unit.

While the use o-f such a resistance known as a discharge resistor located near the control switch, is quite satisfactory during normal operation of a high powered direct current electro-magnet, it does not protect a universally movable lifting magnet against serious damage in cases where the electric current supply conductors are accidentally severed at points between the control switch and the magnet unit. Such accidental severance of the conductor cord frequently occurs when the lifting magnet is handling sharp and jagged pieces of scrap iron some of which are often thrown high in the air when the load is dropped, or may be otherwise brought into contact with the conductor cable.

lt is therefore an important object of the present invention to positively eliminate danger of damaging the insulation of the coils of an electrically energized universally movable lifting magnet whenever the supply current is either willfully or accidentally interrupted.

Another important object of this invention is to provide an improved electric lifting magnet unit wherein the electrical equipment for energizing the magnet is most effectively protected at all times by means of a discharge resistor mounted directly upon the portable unit, preferably in addition to the resistor normally provided at the main control switch.

A further important object of the invention is to provide a direct current universally movable lifting magnet having energizing windings protected by insulation and supplied with electric current through exible conductors, and wherein a resistance for counter electro-motive force induced within the windings in case of severance of the conductors is applied directly across the terminals of these windings remote from the control switch.

Still another important robject `of my invention is to provide an improved lifting magnet which is simple and durable in construction, and highly reliable and efficient in operation.

These and other more specific objects and advantages of the invention will be apparent from the following detailed description from which it will be apparent that the gist of the improvement is the provision of an auxiliary insulation protective resistor applied directly to the terminals of the energizing electric coils of a portable lifting magnet, for positively preventing counter electromotive force or current from damaging the insulation whenever the magnet energizing current is interrupted.

A clear conception of a typical embodiment of the improvement in an electrically energized lifting magnet, may be had by referring to the drawing accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.

Fig. l is a transverse vertical section through an electrically energized portable lifting magnet having an auxiliary discharge resistor shown diagrammatically but mounted directly upon the unit and connecting the terminals `of the magnet energizing coils, the section having been taken approximately along the irregular line 1-1 of Fig. 2;

Fig. 2 is a fragmentary top View of the lifting magnet unit shown in Fig. 1, also showing the discharge resistor diagrammatically and mounted directly upon the magnet but with the cable guard plates removed; and

Fig. 3 is a side elevation of a lifting magnet installation showing the same in operation while removing scrap iron from a railroad car or the like.

While the invention has been shown and described herein as having been embodied in a typical high power direct current lifting magnet of a specific type, it is not my desire or intent to unnecessarily restrict its use to such type of magnet; and it is also contemplated that specific descriptive terms used herein be given the broadest possible interpretation consistent with the disclosure.

Referring to the drawings, the high intensity lifting magnet shown in detail in Figs. l and 2, comprises in general an annular magnet body 5 having outer and inner annular downwardly directed poles 6, 7 respectively of magnetic material firmly attached to its lower face; a spirally wound strip-copper energizing coil 8 insulated externally and between successive layers of its windings by layers 9 of asbestos and mica insulation, and being confined within the annular lower recess of the body 5 by a non-magnetic plate or disc 16 and by a manganese coil-shield 11; a terminal box 12 mounted directly upon the top of the body 5 and enclosing the coil terminals 13; a flexible conductor cable 14 having therein electrical conductors l5 connected to the terminals i3, the cable 14 extending across the top of the body 5 and being shielded by removable guard plates iti; a discharge resistor 17 housed within a casing 18 also carried by the body 5 and being connected across the winding terminals i3 within the terminal box l2; and a series of magnet suspension pins 19 mounted in sturdy upstanding lateraily spaced lugs 20 formed on the top of the body 5 and adapted to receive suspension chains 21 secured to a ring 22 connected to the upper ends of the chains 21, the

box 12 and casing 18 preferably being disposed in thev space between adjacent lugs 20.

When in use, the magnet is ordinarily suspended from a crane or swing boom 24 as shown in Fig. 3, by means of a tackle block 25 coacting with the ring 2.2 and with a lifting and lowering cable 26 riding upon a pulley Zf at the uppe end of the boom 24, and also by means of a cable 29 coacting with an opening 39 in one of th lugs Ztl remote from the resistor l? and which is operable to move the magnet unit laterally. ',The conductor cable lli is also cooperable with a take-up reel El carried by the boom 24 in order to eliminate excessive slack therein, and the magnet manipulating cables are operable by mechanism including a main control switch and discharge resistor located near this switch within a turret or cab 32 in order to effect universal movement of the suspended magnet body e in any direction. When thus installed, the lifting magnet 4may be manipulated to either load or unload diverse scrap iron 33 with respect to a railroad car or a truck body 34 as illustrated, or to transfer other kinds of magnetic material from place to place in a well known manner.

Assuming that the magnet unit has been thus properly installed in a typical scrap handling installation, when the coil 8 is energized and the poles 6, 7 are brought into engagement with the scrap iron 33, numerous pieces of the material will be attracted and firmly held against the lower face of the magnet. The cable 26 may then be manipulated to lift the clinging load, whereupon the other cable 29 and the boom 24 may also be manipulated to transfer the load laterally away from the source of supply. The load of adhering scrap iron 33 may subsequently be dropped by merely opening the control switch and thereby the deenergizing coil 8, but when this is done and due to the high intensity of the electric current used to operate the electro-magnet, considerable counter electromotive force will be created in the windings of the coil 8. rhis counter current is normally quickly dissipated by the main discharge resistor associated with the main control switch and which is connected in parallel with the windings of the coil S, before any damage is done to the insulation 9, and the operations of lifting, transferring and dropping the successive loads may thus be carried on with utmost safety.

When such an electrically energized lifting magnet inlstallation is utilized to handle scrap iron 33, great care is usually exercised to prevent pieces of the material from contacting the conductor cable 1d; but in spite of this fact and because such material often embodies sharp and jagged resilient pieces which bounce to considerable height and in all directions when falling upon the ground or upon other hard surfaces, these sharp pieces do frequently strike the cable lll and sever the same, thereby interrupting the magnet energizing current while the control switch remains closed. lf only the main discharge resistor located within the cab 32 near the control switch is utilized and relied upon, such accidental severance of the conductor cable ld does not permit the resistor to protect the coil insulation 9 against serious damage, and such damage is definitely and effectively avoided by mounting the auxiliary discharge resistor 17 directly upon the top of the magnet body 5 as near as possible to the coil terminals l between the adjacent sturdy lugs 2d and within a protective housing 13. The resistor l may be of any suitable type such as the well known "fhyrite discharge resistor, which automatically dissipates the counter elec-- tro-motive force created within the coil whenever the latter is accidentally deenergized, and which does not interfere with the normal operation of the control switch and main resistor.

From the foregoing detailed description it will be apparent that the present invention provides an improved lifting magnet assemblage which is simple, compact and durable in construction, and wherein the energizing coil insulation 9 is thoroughly protected against damage by counter currents in the coil 8 created either during normal operation of the control switch or by accidental severance of the current supply cable. The invention is primarily applicable to high intensity electro-magnets operable with power consumptions above 7G() watts, and is especially useful in conjunction with universally movable lifting magnets for handling scrap iron 33 and similar materials embodying sharp and jagged resilient pieces. The invention has proven highly satisfactory and advan tageous, and serves to vastly prolong the life of the coil insulation 9.

lt should be understood that it is not desired to limit this invention to the exact details of construction of the electrically energized lifting magnet herein shot-.vn and described for various modifications within the scope of the appended claims may occur to persons skilled in the art.

l claim:

l. ln an electrically energized lifting magnet installation having a main control switch and counter current discharge resistor disposed at a station remote from the magnet, a magnet body having spaced lower lifting poles and an energizing coil provided with electric current supply terminals carried by the body, means for suspending said body to permit universal l .overnent thereof, flexible conductors for supplying current to said coil from a remote source through said terminals, and. an auxiliary discharge resistor for dissipating counter currents in said coil mounted directly upon said universally movable body and being connected to said terminals, said auxiliary resistor being operable upon severance of said conductors between said magnet and the main resistor.

2. In an electrically energized lifting magnet installation having a main control switch and counter current discharge resistor disposed at a vstation remote from the magnet, a magnet body having annular coaxial lifting poles at its bottom and an annular energizing coil conlined therein and provided with curret supply terminals near the top of the body, means suspending said body for universal movement, flexible conductors for energizing said coil from a remote source through said terminals, and an auxiliary discharge resistor carried by said universally movable body and being interposed between said terminals, said auxiliary resistor being operable upon severance of said conductors between said magnet and the main resistor.

3. ln an electrically energized lifting magnet installation having a main control switch and counter' current discharge resistor disposed at a station remote from the magnet, a magnet body having annular coaxial lifting poles at its bottom and an annular energizing coil confined therein and provided with current supply terminals near the top of the body, means suspending said body for universal movement, flexible conductors for energizing `said coil from a remote source through sai terminals, and an auxiliary discharge resistor mounted directly upon said body and being connected to said conductors in parallel with said terminals, said auxi a resistor being operable upon severance of said condr tors between said magnet and the resistor.

4. In an electrically enregized lifting magnet installation having a main control switch and counter current discharge resistor disposed at a station remote from the magnet, a magnet body suspended for universal movevment and having therein an insulated energizing coil, a

flexible conductor cable for sup4 ty g current to said coil from a remote source, and an auxiliary discharge resistor carried directly by said body and being connected to said cable in parallel with said coil, said auxiliary resistor being operable upon severance of said cable between said magnet and the main resistor.

v5. In an electrically energized lifting magnet installation having a main control switch disposed at a station remote from the magnet, a magnet body having lower coaxial lifting poles energized by a coil interposed therebetween and also having upstanding laterally spaced upper lugs, said coil being provided with current supply terminals between adjacent lugs, means connected to said lugs and suspending said body for universal movement, a flexible conductor connecting the main control switch with said terminals, and a discharge resistor for said coil carried directly by said body between said adjacent lugs and being connected to said conductor and said coil across said terminals.

6. In an electrically energized lifting magnet installation having a main control switch disposed at a station remote from the magnet, a magnet body having lower annular inner and outer lifting poles energized by an intervening annular coil provided with current supply terminals at one side of the body, means for suspending said body from above for universal movement, a flexible current supply cable extending from the control switch across the top of said body and being connected to said terminals, and a discharge resistor for said coil carried directly by said body and bridging said terminals in parallel.

References Cited in the file of this patent UNITED STATES PATENTS 833,207 Frank Oct. 16, 1906 960,995 Motz .Tune 7, 1910 1,242,763 Bossu Oct. 9, 1917 1,312,295 Apple Aug. 5, 1919 1,551,752 Kriesel Sept. 1, 1925 1,859,125 Bethenod May 17, 1932 1,923,311 Hodgson Aug. 22, 1933 

